Graphene pattern and process of preparing the same

ABSTRACT

Provided are a graphene pattern and a process of preparing the same. Graphene is patterned in a predetermined shape on a substrate to form the graphene pattern. The graphene pattern can be formed by forming a graphitizing catalyst pattern on a substrate, contacting a carbonaceous material with the graphitizing catalyst and heat-treating the resultant.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2007-0094895, filed on Sep. 18, 2007 and 10-2008-0023458, filed onMar. 13, 2008, in the Korean Intellectual Property Office, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a graphene pattern and a process ofpreparing the same, and more particularly, to a graphene pattern formedin a predetermined shape on a substrate and a process of easilypreparing the graphene pattern.

2. Description of the Related Art

Generally, graphite is a stack of two-dimensional graphene sheets formedfrom a planar array of carbon atoms bonded into hexagonal structures.Recently, as a result of testing properties of single-layered orseveral-layered graphene sheets, their beneficial properties have beenrevealed.

The most noticeable beneficial property is that electrons flow in agraphene sheet as if they are weightless, which means that electronsflow at the velocity of light in a vacuum. In addition, an unusualhalf-integer quantum hall effect for both electrons and holes isobserved in the graphene sheet.

An electron mobility of known graphene sheets is about from 20,000 to50,000 cm²/Vs. Also, it is advantageous to use graphene sheets sinceproducts made from graphite are inexpensive while products made fromcarbon nanotubes which are similar to graphene sheets are expensive dueto low yields obtained during synthesis and purification processes eventhough the carbon nanotubes are inexpensive themselves. Single wallcarbon nanotubes exhibit different metallic and semiconductingcharacteristics according to their chirality and diameter. Furthermore,single wall carbon nanotubes having identical semiconductingcharacteristics have different energy band gaps depending on theirchirality and diameter. Thus, single wall carbon nanotubes are requiredto be separated from each other in order to obtain desiredsemiconducting or metallic characteristics. However, separating singlewall carbon nanotubes is not a simple process.

On the other hand, it is advantageous to use graphene sheets since adevice can be easily designed to exhibit desired electricalcharacteristics by arranging the crystalline orientation in a desireddirection since electrical characteristics of a graphene sheet arechanged according to the crystalline orientation. The characteristics ofthe graphene sheet can be efficiently applied to carbonaceous electricaldevices or carbonaceous electromagnetic devices in the future.

However, although the graphene sheet has these advantageouscharacteristics, a method of economically and reproducibly preparing alarge-area graphene sheet has not been developed yet. The methods ofpreparing a graphene sheet are classified into a micromechanical methodand a SiC thermal decomposition. According to the micromechanicalmethod, a graphene sheet separated from graphite can be prepared on thesurface of a Scotch™ tape by attaching the tape to a graphite sample anddetaching the tape. In this case, the separated graphene sheet does notinclude a uniform number of layers, and does not have a uniform shape ofripped portions. Furthermore, a large-area graphene sheet cannot beprepared. Also, according to the SiC thermal decomposition, a SiC singlecrystal is heated to remove Si by decomposition of the SiC on thesurface thereof, and then residual carbon C forms a graphene sheet.However, the SiC single crystal which is used as a starting materialused in the SiC thermal decomposition is very expensive, and alarge-area graphene sheet cannot be easily prepared.

Therefore, it is not easy to prepare a graphene sheet, and the graphenesheet cannot be easily patterned on a substrate.

SUMMARY OF THE INVENTION

The present invention provides a graphene pattern formed in apredetermined shape on a substrate.

The present invention also provides a process of preparing the graphenepattern.

According to an aspect of the present invention, there is provided agraphene pattern formed of 1-300 layered graphene which is a polycyclicaromatic molecule in which a plurality of carbon atoms are covalentlybound to each other and formed on at least one surface of a substrate.

Graphene constituting the graphene pattern may have a single crystallinestructure, and a peak ratio of D band/G band may be equal to or lessthan 0.2, and preferably 0 (zero) when a Raman spectrum of the grapheneis measured.

According to another aspect of the present invention, there is provideda process of preparing a graphene pattern, the process including:

preparing a substrate on at least one surface of which a graphitizingcatalyst pattern is formed;

contacting a carbonaceous material with the substrate on which thegraphitizing catalyst pattern is formed; and

forming graphene on the graphitizing catalyst pattern throughheat-treatment in an inert or reductive atmosphere.

In the process, the carbonaceous material may be a carbon-containingpolymer, a gaseous carbonaceous material, or a liquid carbonaceousmaterial.

According to another aspect of the present invention, there is provideda process of preparing a graphene pattern, the process including:

preparing a substrate on at least one surface of which a graphitizingcatalyst is formed;

contacting a carbonaceous material with the substrate; and

forming a graphene pattern by selectively heat-treating the carbonaceousmaterial in a predetermined pattern shape in an inert or reductiveatmosphere.

In the process, the carbonaceous material may be a carbon-containingpolymer, a gaseous carbonaceous material or a liquid carbonaceousmaterial.

In the process, the graphitizing catalyst has a single crystallinestructure.

In the process, the contacting the carbonaceous material with thesubstrate may be performed by: (a) coating a carbon-containing polymeras a carbonaceous material on the substrate on which the pattern isformed; (b) introducing a gaseous carbonaceous material as acarbonaceous material onto the substrate on which the pattern is formed;or (c) immersing the substrate on which the pattern is formed in aliquid carbonaceous material as a carbonaceous material andpre-heat-treating the resultant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 schematically shows a process of preparing a graphene patternaccording to an embodiment of the present invention;

FIG. 2 schematically shows a polymer coated on a graphitizing catalyst;

FIG. 3 schematically shows a structure of graphene formed on agraphitizing catalyst;

FIG. 4 schematically shows a process of preparing a graphene patternaccording to an embodiment of the present invention;

FIG. 5 schematically shows a stack of polymers formed on thegraphitizing catalyst and having a hydrophilic part and a hydrophobicpart;

FIG. 6 schematically shows a process of preparing a graphene patternaccording to an embodiment of the present invention;

FIG. 7 schematically shows a process of preparing a graphene patternaccording to an embodiment of the present invention;

FIG. 8 is a scanning electron microscope (SEM) image of a graphenestructure prepared according to Example 4;

FIG. 9 is a SEM image of a silicon substrate structure on which Niparticles prepared according to Example 4 are coated; and

FIG. 10 is a SEM image of a ZnO wire structure on which Ni particlesprepared according to Example 4 are coated.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will now be described more fully withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown.

Graphene having excellent electrical properties is formed on a substratein a shape of a pattern to prepare a graphene pattern according to thepresent invention.

The “graphene” used herein indicates a polycyclic aromatic molecule inwhich a plurality of carbon atoms are covalently bound to each other.The covalently bound carbon atoms usually form 6-membered rings as arepeating unit, but can form 5-membered rings and/or 7-membered rings.Accordingly, in the graphene it appears as if the covalently boundcarbon atoms (usually, sp² bond) form a single layer. The graphene mayhave not only a single layer, but also a plurality of layers up to athickness of 100 nm. Generally, the side ends of the graphene aresaturated with hydrogen atoms.

The graphene may be formed on a substrate, for example on a silicasubstrate, and a graphene pattern is formed in a desired shape at apredetermined portion. Thus, a graphene pattern can be efficientlyapplied to a carbonaceous electronic device, or the like by designing acircuit using graphene having excellent electric characteristics.

The graphene patter formed on the substrate may have 1-300 layers. Whenthe number of the layers of the graphene pattern is greater than 300,electrical characteristics of the graphene may be deteriorated.

A graphitizing catalyst layer having a pattern similar to the graphenepattern may be interposed between the substrate and the graphenepattern. Since the graphitizing catalyst layer is formed during theformation of the graphene pattern, the graphene pattern may directly bein contact with the substrate when the graphitizing catalyst layer isremoved by an acid-treatment, or the like, if desired, or the substrate,the graphitizing catalyst and the graphene pattern are sequentiallystacked when the acid-treatment is not applied.

Examples of the substrate on which the graphene pattern is formed are:an inorganic substrate such as a Si substrate, a glass substrate and aGaN substrate; a plastic substrate such as PET, PES and PEN; and a metalsubstrate such as Ni, Cu and W, but are not limited thereto.

The graphitizing metal catalyst constituting the graphitizing catalystlayer may have a polycrystalline or single crystalline structure. Thepolycrystalline graphitizing metal catalyst can easily form a catalystlayer and is inexpensive. In addition, when the single crystallinestructure is used as the graphitizing metal catalyst, a uniform graphenepattern can be formed since grains which are formed in a polycrystallinestructure are not formed, and thus the graphene formation speed is thesame throughout the entire surface.

The uniformity of the graphene can be identified by a Raman spectrum,particularly, by the presence of D band. D band intensity of a Ramanspectrum indicates the presence of defects formed in the graphene. Astrong D band peak may indicate a lot of defects in the graphene, and aweak D band peak or no D band peak may indicate few defects.

A peak ratio of D band/G band of the graphene sheet prepared by a stackformation method using a graphitizing metal catalyst may be equal to orless than 0.2, preferably equal to or less than 0.01, more preferablyequal to or less than 0.001, and most preferably “0 (zero)” whichindicates that there is few defects in the graphene.

The graphitizing metal catalyst assists carbon atoms to be bound to eachother to form a planar hexagonal structure. Any catalyst used tosynthesize graphite, induce carbonization or prepare carbon nanotubescan be used as the graphitizing catalyst. Examples of the graphitizingcatalyst are at least one metal of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg,Mn, Mo, Rh, Si, Ta, Ti, W, U, V and Zr or an alloy thereof.

The single crystalline graphitizing metal catalyst may be prepared bysingle-crystallize the metal or the alloy, or a commercially availablesingle crystalline metal may be used. Typically, the commerciallyavailable single crystalline metal is formed in a rod shape which can becut into thin films in the form of a sheet to be used.

The graphene pattern described above may be prepared by a process shownbelow.

FIG. 1 schematically shows a process of preparing a graphene patternaccording to an embodiment of the present invention. A substrate on atleast one surface of which a graphitizing catalyst pattern is formed isprepared, a carbonaceous material as a carbon source is contacted withthe substrate on which the graphitizing catalyst pattern is formed, andgraphene is formed on the graphitizing catalyst pattern byheat-treatment in an inert or reductive atmosphere to form a graphenepattern on the substrate.

In the process, any metal-patterning method that is commonly used in theart may be applied to prepare the graphitizing catalyst pattern on thesubstrate without limitation. For example, the graphitizing catalystpattern may be formed on a substrate in a predetermined shape using aprinting or in a high-precision pattern shape using a photolithographyprocess.

In an example of a method of forming a graphitizing catalyst patternaccording to the photolithography process, a high-precision patternshape is formed by depositing a graphitizing catalyst on the entiresurface of a substrate, forming a photoresist layer on the deposition,closely disposing a photomask to the photoresist layer and exposing andetching the resultant.

A carbonaceous material is contacted with the substrate after formingthe graphitizing catalyst pattern. The contacting the carbonaceousmaterial with the substrate may be performed by: (a) coating acarbon-containing polymer as a carbonaceous material on the substrate onwhich the pattern is formed; (b) introducing a gaseous carbonaceousmaterial as a carbonaceous material onto the substrate on which thepattern is formed; or (c) immersing the substrate on which the patternis formed in a liquid carbonaceous material as a carbonaceous materialand pre-heat-treating the resultant.

The carbonaceous material contacted with the graphitizing catalyst toform the graphene pattern may have any structure and any compositionincluding carbon without limitation. The carbonaceous material thatforms a dense coating can be used in order to form a dense graphitelayer.

The carbonaceous material may be a carbon-containing polymer, a gaseouscarbonaceous material, or a liquid carbonaceous material.

Any carbon-containing polymer may be used as the carbonaceous materialwithout limitation. However, the self-assembling polymer is preferablyused as the carbonaceous material since it is regularly arrangedvertically extending from the surface of the graphitizing catalyst asshown in FIG. 2 and forms a graphene pattern having a high density asshown in FIG. 3.

The self-assembling polymer that forms a self-assembling layer may be atleast one polymer selected from the group consisting of an amphiphilicpolymer, a liquid crystal polymer and a conductive polymer.

The amphiphilic polymer includes a hydrophilic group and a hydrophobicgroup, and thus can be arranged in a constant direction in an aqueoussolution. For example, Langmuir-Blodgett arrangements, dippingarrangements and spin arrangements are possible. The amphiphilic polymerincludes a hydrophilic group having at least one of an amino group, ahydroxyl group, a carboxyl group, a sulfate group, a sulfonate group, aphosphate group and salts thereof; and a hydrophobic group having atleast one of a halogen atom, a C1-C30 alkyl group, a C1-C30 halogenatedalkyl group, a C2-C30 alkenyl group, a C2-C30 halogenated alkenyl group,a C2-C30 alkynyl group, a C2-C30 halogenated alkynyl group, a C1-C30alkoxy group, a C1-C30 halogenated alkoxy group, a C1-C30 hetero alkylgroup, a C1-C30 halogenated hetero alkyl group, a C6-C30 aryl group, aC6-C30 halogenated aryl group, a C7-C30 arylalkyl group and a C7-C30halogenated arylalkyl group. Examples of the amphiphilic polymer arecapric acid, lauric acid, palmitic acid, stearic acid, myristoleic acid,palmitolic acid, oleic acid, stearidonic acid, linolenic acid, caprylamine, lauryl amine, stearyl amine and oleyl amine.

The liquid crystal polymer can be arranged in a direction in a liquidstate. The conductive polymer is dissolved in a solvent to form amembrane and can form a crystalline structure by being aligned after thesolvent is evaporated. Thus, the polymers can be aligned by dippingarrangements, spin coating arrangements, or the like. Examples of thepolymer are polyacetylene, polypyrrole, polythiophene, polyanilline,polyfluorene, poly(3-hexylthiophene), polynaphthalene, poly(p-phenylenesulfide) and poly(p-phenylene vinylene).

Meanwhile, a polymer that is automatically aligned in a direction whendeposited from vapor state, for example, a conductive polymer formedusing deposition can also be used herein. Examples of the conductivepolymer are acene and its derivatives, anthracene and its derivatives,hetero anthracene (e.g., benzodithiophene and dithienothiophene) and itsderivatives, tetracene and its derivatives (e.g., halogenated tetracene,tetracene derivatives having a polar substituent, tetracene-thiophenehybrid materials, rubrene and alkyl-, and alkoxy-substituted tetracene),hetero tetracene and its derivatives, pentacene and its derivatives(e.g., alkyl- and halogen-substituted pentacene, aryl-substitutedpentacene, alkynyl-substituted pentacene, alkynyl-substituted alkyl andalkynyl pentacene and alkynyl-substituted pentacene ether), heteropentacene and its derivatives and hetero acene and its derivatives.

The carbon-containing polymer may include at least one polymerizablefunctional group capable of forming a carbon-carbon double bond ortriple bond. The polymerizable functional group can inducepolymerization of polymers through a process of polymerization such asUV irradiation after a layer is formed. Since thus formed carbonaceousmaterial has a large molecular weight, evaporation of carbon can beprevented during the heat-treatment of the polymer.

The polymerization of the carbon-containing polymer may be performedbefore or after coating the polymer on the graphitizing catalyst. Thatis, when the polymerization is induced among the carbon-containingpolymers before coating the polymer on the graphitizing catalyst, acarbonaceous material layer can be formed by transferring a polymerlayer prepared by polymerization to the graphitizing catalyst. Thepolymerization and transfer can be repeated several times to control thethickness of the graphene sheet.

The carbon-containing polymer can be aligned on the surface of thegraphitizing catalyst using various coating methods, such asLangmuir-Blodgett, dip coating, spin coating and vacuum deposition. Inparticular, the carbon-containing polymer may be coated on the entiresurface of the substrate or selectively coated on the graphitizingcatalyst using the coating methods.

When the carbon-containing polymer is selectively coated on thegraphitizing catalyst, the polymer has an identical or a similar patternto the patternized graphitizing catalyst. Even when thecarbon-containing polymer is coated on the entire surface of thesubstrate as shown in FIG. 4, the carbon-containing polymer that iscoated on a region on which the graphitizing catalyst is not coated isnot affected by the graphitizing catalyst during the heat-treatment, andthus it is thermally decomposed to be evaporated or forms amorphouscarbon. The amorphous carbon may be selectively removed duringsubsequent processes.

Meanwhile, the molecular weight of the carbon-containing polymer,thickness of the polymer layer or the number of self-assembling polymerlayers may vary depending on a desired number of layers of the graphene.That is, use of a carbon-containing polymer having a large molecularweight increases the number of layers of the graphene since the polymerhas a large amount of carbon. As the thickness of the polymer layerincreases, the number of layers of the graphene is increased, and thusthe thickness of the graphene is also increased. The thickness of thegraphene can be controlled using the molecular weight and the amount ofthe carbon-containing polymer.

In addition, the amphiphilic polymer which is a self-assembling polymerincludes a hydrophilic part and a hydrophobic part in one molecule. Asshown in FIG. 5, the hydrophilic part of the polymer is combined withthe hydrophilic graphitizing catalyst to be uniformly aligned on thecatalyst layer, and the hydrophobic part of the amphiphilic polymer isaligned in the opposite direction to be combined with the hydrophilicpart of another amphiphilic polymer that is not combined with thecatalyst layer. When the amount of the amphiphilic polymer issufficient, the amphiphilic polymer can be stacked on the catalyst layerby the hydrophilic-hydrophobic bonds. The stacked layers formed of aplurality of the amphiphilic polymers can form a graphene layer byheat-treatment. Thus, a graphene pattern having a desired thickness canbe prepared since the number of layers of the graphene can be controlledby selecting an appropriate amphiphilic polymer and adjusting the amountof the amphiphilic polymer.

Meanwhile, the gaseous carbonaceous material used as the carbonaceousmaterial source is thermally decomposed by contacting with thegraphitizing catalyst on the substrate to form graphene. Any materialthat can supply carbon and be in the gas phase at 300° C. or higher maybe used as the gaseous carbonaceous material without limitation. Thegaseous carbonaceous material may be a compound containing carbon,preferably 6 or less carbon atoms, more preferably 4 or less carbonatoms, and most preferably 2 or less carbon atoms. The compoundcontaining carbon may include at least one selected from the groupconsisting of carbon monoxide, ethane, ethylene, ethanol, acetylene,propane, propylene, butane, butadiene, pentane, pentene,cyclopentadiene, hexane, cyclohexane, benzene and toluene.

The gaseous carbonaceous material may be introduced to a chamberincluding a graphitizing catalyst at a constant pressure. The chambermay only include the gaseous carbonaceous material, or further includean inert gas such as helium and argon.

In addition, hydrogen may be used with the gaseous carbon material inorder to control gaseous reactions by cleaning the surface of a metalcatalyst. The amount of the hydrogen may be in the range of 5 to 40% byvolume, preferably 10 to 30% by volume, and more preferably 15 to 25% byvolume based on the total volume of the chamber.

In addition, a liquid carbonaceous material used as the carbonaceousmaterial is contacted with a substrate on which a graphitizing catalystis formed, and the substrate is pre-heat-treated. Carbon thermallydecomposed by the pre-heat-treatment is infiltrated into thegraphitizing catalyst through a carborization process. The substrate maybe immersed in the liquid carbonaceous material for the contact process.

The liquid carbonaceous material may be an organic solvent. Any organicsolvent that can contain carbon and thermally decomposed by thegraphitizing catalyst can be used without limitation. A polar ornonpolar organic solvent having a boiling point in the range of 60 to400° C. may be used. The organic solvent may be an alcohol-based organicsolvent, an ether-based organic solvent, a ketone-based organic solvent,an ester-based organic solvent, an organic acid solvent, or the like.Among these, the alcohol-based and ether-based organic solvents arepreferably used since they have superior reactivity and reducing powerand the graphitizing metal catalyst can be easily adsorbed to thesolvents. Monohydric alcohols and polyhydric alcohols may be used aloneor in combination as the alcohol-based organic solvent. Examples of themonohydric alcohol are propanol, pentanol, hexanol, heptanol andoctanol. Examples of the polyhydric alcohol are propylene glycol,diethylene glycol, dipropylene glycol, triethylene glycol, tripropyleneglycol, octylene glycol, tetraethylene glycol, neopentyl glycol,1,2-butanediol, 1,3-butanediol, 2,3-butanediol,dimethyl-2,2-butanediol-1-1,2 and dimethyl-2,2-butanediol-1,3. Themonohydric alcohols and polyhydric alcohols may have an ether group inaddition to a hydroxyl group.

The liquid carbonaceous material may be used alone, or may furtherinclude a base. When a base is added to the liquid carbonaceousmaterial, carburization speed may be increased. Thus, time required forthe graphene formation may be reduced, and flocculation of particles maybe prevented by increasing viscosity. The base may be added theretoalone, or with water to increase solubility. The base may be an organicand/or inorganic base, and examples of the base are tetramethyl ammoniumchloride (TMAH), sodium hydroxide and potassium hydroxide. Theconcentration of the base may be in the range of 0.01 to 5.0 M in theorganic solvent, but is not limited thereto. When the concentration ofthe base is less than 0.01 M, carburization speed is too slow, andflocculation of particles may not be controlled. On the other hand, whenthe concentration of the base is greater than 5.0 M, the viscosity istoo high so that particles may not be separated from the solvent and maynot be washed.

When the liquid carbonaceous material is used, carburization may beperformed through the pre-heat-treatment. The liquid carbonaceousmaterial is thermally decomposed by the graphitizing catalyst during thepre-heat-treatment. The thermal decomposition of the liquid carbonaceousmaterial by the graphitizing catalyst is disclosed in Nature, vol 418,page 964. For example, the resultant products of the thermaldecomposition of the organic solvent such as the polyhydric alcohol arealkanes, H₂, CO₂, H₂O, etc. Carbon elements among the resultant productsare carburized into the catalyst. The disclosure is incorporated hereinby reference.

The pre-heat-treatment for the thermal decomposition may be performedwhile stirring to sufficiently mix the liquid carbonaceous material andthe catalyst at 100 to 400° C. for 10 minutes to 24 hours. When thepre-heat-treatment is performed at less than 100° C., the organicsolvent may not be sufficiently thermally decomposed. On the other hand,when the pre-heat-treatment is performed at greater than 100° C.,particles may be melted and flocculated. When the pre-heat-treatment isperformed for less than 10 minutes, the organic solvent may not besufficiently thermally decomposed. On the other hand, when thepre-heat-treatment is performed for more than 24 hours, thepre-heat-treatment is not economical.

Meanwhile, the carbon content in the catalyst may be controlled bycontrolling the degree of carburization, and thus the thickness of thegraphene layer formed in a subsequent process can be controlled. Forexample, when a liquid carbonaceous material which is easily thermallydecomposed is used, the amount of decomposed carbon is increased, sothat a large amount of carbon can be carburized into the catalyst. Inaddition, carbon content carburized into the catalyst can be controlledby regulating the carburization process by controlling the temperatureand time of the heat-treatment. As a result, the degree of grapheneformation can also be controlled, so that the thickness of the graphenelayer can be controlled.

Graphene constituting the graphene pattern may be a stack of a pluralityof layers, preferably 1-300 layers, and more preferably 1-60 layers. Thegraphene having 300 layers or greater is regarded not as graphene but asgraphite, which is not within the scope of the present invention.

Carbonaceous materials such as a carbon-containing polymer, a liquidcarbonaceous material and a gaseous carbonaceous material are contactedwith the graphitizing catalyst and the resultant is heat-treated tographitize the carbonaceous material. The heat-treatment can beperformed in an inert or reductive atmosphere in order to preventoxidation of the elements of the carbonaceous material. Carbon atoms inthe organic material are covalently bound to each other through theheat-treatment and form, for example, a planar hexagonal structure toform graphene on the substrate.

The heat-treatment is performed at a temperature in the range of 400 to2,000° C. When the temperature is lower than 400° C., the graphitizationcannot be sufficiently performed. On the other hand, when thetemperature is higher than 2,000° C., carbon may be evaporated. Theheat-treatment may be performed for 0.1 to 10 hours. When theheat-treatment time is not within the range described above, thegraphitization cannot be sufficiently performed or economical efficiencymay be decreased.

The heat-treatment may be performed by induction heatings, radiantheats, lasers, infrared rays (IR), microwaves, plasma, ultraviolet (UV)rays or surface plasmon heatings without limitation.

After the heat-treatment, the heat-treated resultant is subject to acooling process. The cooling process is required to uniformly grow andregularly arrange the formed graphene. Since rapid cooling may causecracks in the graphene sheet, the heat-treated graphene may be graduallycooled. For example, the heat-treated graphene may be cooled at a rateof 0.1-10° C./min or naturally cooled. In a natural cooling process, aheat source is removed. In this regard, a sufficient cooling rate can beobtained only by removing the heat source.

According to the process of preparing a graphene pattern describedabove, a pattern of a graphitizing catalyst is formed, and then agraphene pattern is formed. Alternatively, a carbonaceous material maybe directly patterned. That is, a graphitizing catalyst is deposited onthe entire surface of a substrate using deposition, or the like, andthen a carbonaceous material may be printed in a predetermined patternwithout patterning the graphitizing catalyst or patterned byheat-treatment.

According to the printing of the carbonaceous material, a carbonaceousmaterial is printed in a high-precision pattern on a substrate on whicha graphitizing catalyst is entirely coated using an inkjet printing, orthe like, and the resultant is heat-treated to form a graphene pattern.

According to the patterning of the carbonaceous material byheat-treatment, a carbonaceous material is contacted with a substrate onwhich a graphitizing catalyst is entirely coated and the carbonaceousmaterial is selectively heated in a pattern shape to form a graphenepattern as shown in FIG. 6. Here, any energy source capable ofpatterning such as electrons, ions, ultraviolet rays, infrared rays,microwaves, and the like may be used without limitation. Since only apredetermined pattern is heated without heating the entire substrate,cracks of graphene which may occur during heat-treating the entirelarge-area substrate may be prevented, and a graphene pattern of plasticmay also be formed on a substrate by controlling heating time andtemperature.

The graphitizing catalyst used in various process of preparing thegraphene pattern may be formed in a particulate shape. That is, thegraphitizing catalyst particles are disposed in a desired shape on asubstrate using dip coating,

Langmuir-Blodgett, spin coating, or the like as shown in FIG. 7. Then, agraphene pattern has a shape of the graphitizing catalyst particles.Alternatively, a graphene pattern having a predetermined shape may beformed by coating an organic material on the surface of the graphitizingcatalyst particles to form a core-shell structure and arranging andheat-treating the core-shell structure on the substrate. The particulategraphitizing catalyst may further include a core such as a metal oxide.

When a graphene pattern-formining process described above is performed,a graphitizing catalyst layer and a graphene pattern are sequentiallyformed on at least one surface of the substrate. Thus, graphitizingcatalyst layer in itself may be used, or if desired, may be removed byan acid-treatment to directly bind the graphene pattern and thesubstrate.

According to a process of preparing a graphene pattern described above,a high-precision graphene pattern can be efficiently prepared in asimple process, and the thickness can be easily controls. Thus, thegraphene pattern can be efficiently applied to various carbonaceouselectronic devices.

The present invention will now be described in greater detail withreference to the following examples. The following examples are forillustrative purposes only and are not intended to limit the scope ofthe invention.

EXAMPLE 1

A photoresist (PR) patterning was formed on a 3 cm×3 cm siliconsubstrate on which 100 nm of SiO₂ is coated, and Ni was deposited usingsputtering to form a Ni high-precision pattern having a line width of 1micron.

An oleic acid solution was separately prepared by dissolving oleic acidin chloroform to a concentration of 1 mg/ml. After water is added to aLB device, 50 μl of the oleic acid solution was dropped thereto. Then, aself assembled monolayer (SAM) was prepared using the LB device. The SAMformed of oleic acid was polymerized by radiating UV rays of awavelength of 254 nm. The polymerized oleic acid SAM was transferred tothe silicon substrate on which 100 nm of SiO₂ is coated.

Then, the oleic acid-coated substrate was dried by heating at 60° C. for12 hours in a vacuum atmosphere. The dried oleic acid-coated substratewas heat-treated in a furnace at 500° C. for 1 hour in a nitrogenatmosphere to obtain a substrate including a single-layered graphenesheet in a predetermined pattern.

Then, the substrate on which the graphene pattern is formed was meltedin 0.1 M HCl for 24 hours to remove the Ni thin film.

EXAMPLE 2

A substrate including a 4-layered graphene pattern was prepared in thesame manner as in Example 1, except that the process of transferring thepolymerized oleic acid SAM to the Ni pattern was repeated 4 times.

Then, the substrate on which the graphene pattern is formed was meltedin 0.1 M HCl for 24 hours to remove the Ni thin film.

EXAMPLE 3

Ni was deposited on a 3 cm×3 cm silicon substrate on which 100 nm ofSiO₂ is coated using sputtering to form a Ni thin film.

An oleic acid solution was separately prepared by dissolving oleic acidin chloroform to a concentration of 1 mg/ml. After water is added to aLB device, 50 μl of the oleic acid solution was dropped thereto. Then, aself assembled monolayer (SAM) was prepared using the LB device. The SAMformed of oleic acid was polymerized by radiating UV rays of awavelength of 254 nm. The polymerized oleic acid SAM was transferred tothe silicon substrate on which 100 nm of SiO₂ is coated. The process oftransferring the polymerized oleic acid SAM to the substrate wasrepeated 4 times.

The substrate was partially heat-treated using e-beam to form a4-layered graphene having a line width of 50 nm, and melted in 0.1 M HClfor 24 hours to remove the oleic acid SAM formed on the region on whichgraphene is not formed and the Ni thin film.

EXAMPLE 4

A 3 cm×3 cm three-dimensional silicon substrate on which 100 nm of SiO₂is coated and a ZnO wire having a diameter of 80 nm and a length ofseveral microns were prepared. The silicon substrate and the ZnO wirewere introduced into an aqueous solution in which APS is dissolved, andthe mixture was stirred, filtered and dried at room temperature for 1hour to prepare a silicon substrate and ZnO wire coated with APS.

An aqueous solution of 5 nm Ni particles coated with mercapto aceticacid was prepared. Each of the silicon substrate coated with APS and theZnO wire coated with APS was introduced into the aqueous solution of Niparticles coated with mercapto acetic acid. Ni nanoparticles arearranged in a single layer on the silicon substrate by dipping thesilicon substrate in an aqueous solution of Ni nanoparticles. Then, theresultants were added to an aqueous solution in which Ni particles aredistributed, and the mixture was stirred, filtered and dried at roomtemperature for 1 hour to obtain a silicon substrate and a ZnO wire onwhich Ni particles are coated in a single layer. FIGS. 9 and 10 are SEMimages of the silicon substrate and the ZnO wire.

Two solutions in which 46.7 g of distilled water and 1.4 g of oleic acidwere prepared. The silicon substrate coated with Ni particles and theZnO wire coated with Ni particles were added to the solutions, and themixtures were stirred at 400 rpm for 5 hours. When the stirring iscompleted, the silicon substrate coated with Ni particles coated witholeic acid and the ZnO wire coated with Ni particles were separated fromeach other by removing water by adding them to filter paper and applyingvacuum. The obtained sample was heated in a vacuum atmosphere at 60° C.for 12 hours to remove residual water from the surface of the Niparticles. Ni particles coated with 5 nm and 3 nm of graphite wereobtained on the surface of each of the silicon substrate and the ZnOwire by heat-treating the dried oleic acid-coated Ni particles innitrogen atmosphere at 500° C. When each of the samples was melted in0.1 M HCl for 24 hours, a silicon substrate and a ZnO wire on whichspherical graphene shell formed of graphene may be prepared.

FIG. 8 is a scanning electron microscope (SEM) image of a graphenestructure prepared according to Example 4. FIG. 9 is a SEM image of athree-dimensional silicon substrate structure on which Ni particlesprepared according to Example 4 are coated. FIG. 10 is a SEM image of aZnO wire structure on which Ni particles prepared according to Example 4are coated.

EXAMPLE 5

A photoresist (PR) patterning was formed on a 3 cm×3 cm siliconsubstrate on which 100 nm of SiO₂ is coated, and Ni was deposited usingsputtering to form a Ni high-precision pattern having a line width of 1micron.

The silicon substrate on which the SiO₂ and Ni high-precision patternwere formed was disposed in a chamber, and heat-treated at 400° C. for20 minutes using a halogen lamp as a heat source while acetylene gas wasadded to the chamber at a constant rate of 200 sccm to form graphene onthe graphitizing catalyst.

Then, a 7 layered graphene sheet was formed by removing the heat sourceand naturally cooling the interior of the chamber to grow graphene in auniform arrangement.

Then, the substrate including the graphene sheet was immersed in 0.1 MHCl for 24 hours to remove the Ni metal pattern.

EXAMPLE 6

A single crystalline Ni in which an oxide is removed was placed in asilicon substrate and a photoresist (PR) patterning was formed on thesingle crystalline Ni, and Ni was removed to form a Ni high-precisionpattern having a line width of 1 micron.

Then, the substrate was heat-treated at 750° C. for 2 minutes using ahalogen lamp heat source while introducing acetylene gas and hydrogengas into the chamber respectively at 5 sccm and 45 sccm to form grapheneon a graphitizing catalyst pattern.

Then, the heat source was removed and the chamber was naturally cooledto grow the graphene to a constant thickness, thereby forming a graphenepattern having about 7 layers.

Then, the substrate on which the graphene sheet is formed was melted in0.1 M HCl for 24 hours to remove the Ni thin film.

A Raman spectrum of the graphene pattern was measured. The formation ofgraphene was identified by G peak shown at 1594 cm⁻¹. In addition,D/G=0.193 was identified by D peak shown at 1360 cm⁻¹.

EXAMPLE 7

A photoresist (PR) patterning was formed on a 3 cm×3 cm siliconsubstrate on which 100 nm of SiO₂ is coated, and Ni was deposited usingsputtering to form a Ni high-precision pattern having a line width of 1micron.

500 ml of diethylene glycol was added to a reactor, 89.7 ml of 25%tetramethyl ammonium chloride (TMAH) aqueous solution was added thereto,and the substrate was immersed in the solution.

Then, the Ni metal pattern was carburized by reacting the substrate withthe solution while mechanically mixing (despa) at 230° C. or more for 4hours. The carburized substrate was separated and dried in a vacuum ovenat 50° C. overnight. The dried carburized substrate was heat-treated inan argon atmosphere at 450° C. for 1 hour to form graphene on thesurface of the Ni pattern.

Then, the substrate on which the graphene is formed was melted in 0.1 MHCl for 24 hours to remove the Ni metal pattern.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A graphene pattern comprising: 1-300 layers of graphene, which is apolycyclic aromatic molecule in which a plurality of carbon atoms arecovalently bound to each other, and wherein the graphene is disposed onat least one surface of a substrate.
 2. The graphene pattern of claim 1,having a single crystalline structure, wherein a D band/G band peakratio is equal to or less than 0.2, when measured in a Raman spectrum ofthe graphene.
 3. The graphene pattern of claim 1, having 1-60 layers ofgraphene.
 4. The graphene pattern of claim 1, further comprising agraphitizing catalyst interposed between the substrate and the graphene.5. The graphene pattern of claim 4, wherein the graphitizing catalyst isat least one selected from the group consisting of Ni, Co, Fe, Pt, Au,Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, Ti, W, U, V and Zr.
 6. A process ofpreparing a graphene pattern, the process comprising: preparing asubstrate on at least one surface of which a graphitizing catalystpattern is formed; contacting a carbonaceous material with the substrateon which the graphene pattern is formed; and forming graphene on thegraphitizing catalyst pattern through heat-treatment in an inert orreductive atmosphere, wherein the carbonaceous material is acarbon-containing polymer, a gaseous carbonaceous material or a liquidcarbonaceous material, and wherein the carbon-containing polymercomprises at least one polymerizable functional group capable of forminga carbon-carbon double bond or triple bond.
 7. (canceled)
 8. The processof claim 6, wherein the graphitizing catalyst has a single crystallinestructure.
 9. The process of claim 6, wherein the contacting thecarbonaceous material with the substrate is performed by: (a) coating acarbon-containing polymer as a carbonaceous material on the substrate onwhich the pattern is formed; (b) introducing a gaseous carbonaceousmaterial as a carbonaceous material onto the substrate on which thepattern is formed; or (c) immersing the substrate on which the patternis formed in a liquid carbonaceous material as a carbonaceous materialand pre-heat-treating the resultant.
 10. The process of claim 6, whereinthe graphitizing catalyst is at least one selected from the groupconsisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta,Ti, W, U, V and Zr.
 11. The process of claim 6, wherein theheat-treatment is performed at a temperature in the range of 400 to2,000° C. for 0.1 to 10 hours.
 12. The process of claim 6, furthercomprising removing the graphitizing catalyst by an acid-treatment afterthe heat-treatment.
 13. A process of preparing a graphene pattern, theprocess comprising: preparing a substrate on at least one surface ofwhich a graphitizing catalyst is formed; contacting a carbonaceousmaterial with the substrate; and forming a graphene pattern byselectively heat-treating the carbonaceous material in a predeterminedpattern shape in an inert or reductive atmosphere, wherein thecarbonaceous material is a carbon-containing polymer, a gaseouscarbonaceous material or a liquid carbonaceous material, and wherein thecarbon-containing polymer comprises at least one polymerizablefunctional group capable of forming a carbon-carbon double bond ortriple bond.
 14. (canceled)
 15. The process of claim 13, wherein thegraphitizing catalyst has a single crystalline structure.
 16. Theprocess of claim 13, wherein the contacting the carbonaceous materialwith the substrate is performed by: (a) coating a carbon-containingpolymer as a carbonaceous material on the substrate on which the patternis formed; (b) introducing a gaseous carbonaceous material as acarbonaceous material onto the substrate on which the pattern is formed;or (c) immersing the substrate on which the pattern is formed in aliquid carbonaceous material as a carbonaceous material andpre-heat-treating the resultant.
 17. The process of claim 13, whereinthe graphitizing catalyst is at least one selected from the groupconsisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta,Ti, W, U, V and Zr.
 18. The process of claim 13, wherein theheat-treatment is performed at a temperature in the range of 400 to2,000° C. for 0.1 to 10 hours.
 19. The process of claim 13, furthercomprising removing the graphitizing catalyst by an acid-treatment afterthe heat-treatment.